Sometimes, on the battlefield, heavy cannon, such as artillery pieces, tanks and the like, are deployed against foot soldiers, particularly where the target is out of range of machine gun bullets, or where there is no line of sight with the target. It will be appreciated however, that very small changes in elevation of the cannon will have a major effect on where a shell will land, and this results in an inherent difficulty in using heavy artillery against soldiers. Furthermore, a company of foot soldiers may be spread out over an area of land, and the damage caused by a conventional shell is too localized to be of much use. One known approach for destroying foot soldiers under these conditions is to use a ‘cargo projectile’ loaded with submunition grenades. The cargo projectile is a shell that is designed to be fired from a large caliber cannon such as a tank or artillery piece over the position of enemy foot soldiers. A plurality of submunition grenades are released and dispersed from the cargo projectile over a large area of ground. Some such submunition grenades are designed to self destruct in the air. Others are designed to explode on impact.
The basic requirements for submunition grenades are (i) a high degree of safety during storage and handling, both prior, during and subsequent to their being packed into cargo projectiles, (ii) reliability during deployment, i.e. that they should explode appropriately after release from the cargo projectile, and not prematurely, prior to their dispersal, and (iii) the number of dangerous dud grenades that do not explode on impact should be minimized. This is most important, as their being scattered over the battlefield poses a hazard to friendly troops and even to civilians or wildlife long after the battle. It will be appreciated that these requirements are to some extent contradictory, and the development of safe but highly explosive ordnance is not trivial.
Each submunition grenade includes a casing that disintegrates into lethal shrapnel when the submunition grenade explodes, a warhead for exploding the casing, and a fuze for detonating the warhead. To achieve the required safety levels in handling and storage, but reliability of the submunition grenade after releasing, the fuzes thereof are sophisticated devices that generally include chemical, mechanical and occasionally electrical subcomponents.
Typically the fuze of an impact type of submunition grenade includes a chemical detonator and a firing pin that triggers the detonator on impact. To allow the grenades and the cargo projectiles that contain such grenades to be handled safely, various safety mechanisms have been devised. Typically, in addition to the armed position in which is the grenade's fuze aligned to trigger the detonator, the firing pin of the submunition grenade also has a safe position, and when the firing pin is in this safe position, the submunition grenade can be handled and even dropped without fear of it detonating. Once the firing pin is moved to the armed position however, an impact or similar jolt will cause the pin to detonate the detonator, igniting the warhead thereby and causing the submunition grenade to explode.
Submunition grenades have been developed that not only are stored with their firing pins in the unarmed position, but their firing pins are only moved to the armed position after launching. In one such mechanism, only after the submunition grenade falls clear of the cargo projectile, the firing pin is brought into the activated position, where, on impact, the pin can detonate the detonator and thereby ignite the lead warhead.
Submunition grenade fuzes are known that have a locked safe position for the firing pin that is designed to prevent the firing pin from being moved to the armed position inadvertently. When the grenades are packed into a cargo projectile carrier, the firing pin of each grenade fuze is unlocked, but it remains in its safe position until the fuze is armed. This only happens after the submunition grenade is ejected from the cargo projectile. In a submunition grenade of this type, one end of the shaft of the firing pin protrudes outside the fuze housing, and to the protruding end a drag producing means is fitted. The cargo projectile warhead spins in flight due to rifling of the barrel of the gun from which it is launched. When the grenades are ejected from the cargo projectile, the drag producing means, typically a nylon ribbon is activated. This drag producing means acts in an inertial manner, countering the spin of the submunition grenade around its longitudinal axis, and displaces the firing pin assembly, causing it to assume a striking position. In his manner, the fuze is armed automatically, but only after ejection. On impact, the firing pin assembly is driven into the grenade with a force that causes the detonation of the fuze detonator and explosion of the warhead thereby.
A known safety mechanism for submunition grenades is a slider assembly that keeps the detonator in a safe position away from the firing pin, preventing inadvertent detonation. After being detached from the cargo projectile, the centrifugal forces on the submunition grenade cause the slider assembly to slide into the armed position, aligning the detonator with the firing pin. Once aligned, a catch locks the slider in place such that upon appropriate impact, such as an impact with a hard surface, the firing pin is driven forward to strike the appropriately aligned detonator, detonating it, thereby igniting the warhead of the submunition grenade.
Like all mechanical systems, such slider assemblies are not fail-safe. Occasionally, they do not retract, or do not retract fully. This can happen, for example, when the striker assembly is locked for some reason.
One disadvantage of the prior art submunition fuzes described hereinabove, is that where the submunition grenade impacts with an inappropriate surface, such as a soft surface, or where the angle of impact is wrong, such that the firing pin is not induced to strike the detonator, the grenade is not detonated.
Consequently, there is a risk of armed submunition grenades launched at the enemy but not detonated on impact being left scattered over the battlefield. Wherever a submunition grenade does not detonate it is considered as being a “dud”. Armed dud submunition grenades remain dangerous, and pose a risk to friendly troops and even to civilians long after the battle.
Thus, despite the many safety features included in submunition grenades, there is still a risk of armed submunition grenades being dispersed but not detonated, and the present invention addresses this risk.